The Clyde McCoy Saga

The Clyde McCoy Clan

I've recently had the rare experience of working on 10 old Vox Clyde McCoy wah-wah pedals. This family of old Clyde McCoys belongs to Billy Corgan of the Smashing Pumpkins.

After checking all the circuit boards in these units I was surprised to find a variation in the basic circuit design. Three of these units had different component values from the well-known Vox design. The dimensions of the inductor coils of these units were slightly different as well. The result is that the range of the wah effect is lower in frequency and not as bright.... I could call it a baritone wah pedal.

Old wah pedals change sound as the resistive track of the potentiometer wears down from constant use and gets thinner. The original value of the pot is 100k and this can increase up to 3 or 4 megohms until the pot finally gives out and becomes an open circuit. If you replace the old pot with a new one the difference can be quite remarkable.

The limited movement of the pedal means that the pot can only operate over two thirds of its full range. The original pot has a custom taper designed to go from 0 to 100% of its value in exactly this limited range. The last 30% is never used. In other words the pot is fully open when it is turned up to 2 thirds and has no further effect if you turn it all the way to the end. This gives you a bit of leeway when you adjust it. If the sound is too bright when the pedal is all the way down you can back off the pot a bit.

By the way, I prefer the more common circuit design since I like the top end.

The Cry Baby Wah-Wah

I just love those old Vox Clyde McCoy's and Cry Baby's, nothing beats them. The only trouble is that they cut a lot of your tone when you switch them off. You can use a buffer pedal before the wah in order to prevent the loss but that makes the wah sound too brite when you switch it on again. Some newer Dunlop wah's have a built-in buffer and suffer from the same aggressive brite effect. If you put the buffer after the wah it's no use, your high's are gone.

So, what's to be done? Well, the problem arises because the input impedance is intentionally low in order to obtain a better wah effect with more tone. The bypass switch, however, only switches the output of the pedal. The low impedance input of the wah is never switched at all and stays connected to your guitar signal all the time, even if you bypass the wah effect. The best solution, therefore, is to replace the bypass switch with a DPDT switch and rewire the pedal for full bypass of both input and output. Then use a buffer pedal after the wah in your chain of effects.

This way there will be no alteration of the wah effect when you use it, and no coloration of your sound when you switch it off.

Cathode Biasing Amps for Class A

About a year and a half ago I decided to convert the output stage of my 50-watt Marshall combo into a self-biasing cathode design. This method of biasing is normally found only in smaller amps because it dissipates a lot of heat in the cathode resistor and is considered to be inefficient. In other words it consumes a bit of more power. The old 20-watt Marshall heads built in the late 60's utilize this method, but all 50 and 100-watt models use fixed biasing. I was trying to reproduce the sound of my little Jaguar (that's my '69, 20-watt head that I totally redesigned and that been refinished in fake leopard skin).

The results were very impressive, the clean sound was now noticeably sweeter and had better sustain. Another benefit was that when the amp was driven to full power under hard clipping, crossover distortion was greatly reduced due to the self-biasing design With hard picking the amp was now less peaky and more compressed. I can't say that I noticed any loss of power. For good measure I installed a pull-switch on the amp in order to compare between the original fixed-biased circuit and my new cathode biased one. I played this amp constantly in all kinds of venues from bars to outdoor blues festivals and I can tell you now that I'm never going back to fixed-bias. To hear a good example of this, try out the Fender Prosonic. There is a switch in the back to select between solid state rectifier, tube rectifier Class AB, and tube rectifier Class A (Cathode-biasing).

Well, now all that remains to try is to see if I can do this safely on a 100-watt model..... can't wait!

New Fender Amp Mod

I'm proud to announce that the new Mod for Fender amps that I've been working on for some time is finally available!!

This new mod does not in any alter the existing sound of the Reverb Vibrato channel of the amp.

I've modify the normal channel into a great sounding overdrive channel with preamp gain and master volume. Select between clean and overdrive using a footswitch. The brite switch selects between medium-gain (Rhythm) and high-gain (Lead) modes.

No holes are drilled in the chassis. No controls (pots) are changed. I've remove 2 input jacks and use the same holes to install new pots for the overdrive channel. This way the amp retains it's original condition and value. If need be it can easily be converted back to it's original wiring.